| DATA_SET_DESCRIPTION |
Data Set Overview
=================
This data set contains Calibrated data taken
by the New Horizons Multispectral Visible Imaging Camera instrument
during the KEM1 ENCOUNTER mission phase.
MVIC is a visible and near-infrared imager. MVIC comprises seven
separate CCD two-dimensional arrays; all rows are 5024 pixels across
with twelve pixels at either end of each row optically inactive. The
single Pan Frame array is a panchromatic frame-transfer imager, 5024x128
pixels, that typically takes multiple frames in each observation. The
common Pan Frame data product is an image cube in three dimensions:
spatial; spatial; image frame, equivalent to time. Of the remaining six
arrays, 5024x32 pixels each, two are panchromatic (unfiltered), and the
remaining four are under filters and called the color arrays:
Near-InfraRed (NIR); methane (CH4); Red; Blue. All six are operated in
Time-Delay Integration (TDI) mode; the TDI arrays are in some ways
similar to line cameras. In TDI mode, the spacecraft and MVIC boresight
are scanned across the target at a rate that matches the charge transfer
clock rate across the rows of the CCDs. Ideally the rates are matched,
so as the charges are read by the analog-to-digital converter off the
last line of the array, each pixel reading is near-proportional to the
brightness of the same piece of the target as its image moved across the
array, accumulating charge on each row. In TDI mode it is the product of
the per-row charge clock rate and the duration of the observation that
determines the number of rows each the image, and the image can be
arbitrarily long; the number of rows (32) in each array is not relevant
in determining the size of the image. The common data product for each
of the TDI arrays is a 2-D image, of arbitrary length as noted earlier.
The 08/31/2018 data was an MVIC Instrument CheckOut targeted at MU69
(Arrokoth). In late December 2018 New Horizons neared MU69, MVIC
collected data for Deep Satellite Searches, Color Scans of MU69, Pan
Scans, Deep Ring Search, and Deep Satellite Search TeaCup. During
departure additional scans and imaging were performed of MU69, Deep
Satellite Searches, Deep Ring Search, and a look back at Pluto.
For a list of observations, refer to the data set index table. This
is typically INDEX.TAB initially in the INDEX/ area of the data set.
There is also a file SLIMINDX.TAB in INDEX/ that summarizes key
information relevant to each observation, including which sequence
was in effect and what target was likely intended for the
observation.
Version
=======
This is VERSION 4.0 of this data set.
This version includes data acquired by the spacecraft between
08/14/2018 and 04/30/2020. It only includes data downlinked before
05/01/2020. Future datasets may include more data acquired by the
spacecraft after 08/13/2018 but downlinked after 04/30/2020.
This version includes MVIC Color and Pan Scans prior to, during, and
after the MU69 encounter. A number of experiments were conducted,
including Ring/Coma Search, Look Back at Pluto, Functional Test,
Radiometric Calibration, Solar Star Calibration, and Color Scan of
Neptune and Uranus.
V3.0
----
Version 3.0 of this dataset included data acquired by the spacecraft
between 08/14/2018 and 07/31/2019. It only included data downlinked
before 08/01/2019.
V2.0
----
Version 2.0 included data acquired by the spacecraft between 08/14/2018
and 01/31/2019. It only included data downlinked before 02/01/2019.
Two digits of precision have also been added to the EXPOSURE_DURATION
value in all data labels after V1.0.
General statement about data set versions after V1.0
----------------------------------------------------
The pipeline (see Processing below) was re-run on these data for each
version since the first (V1.0). A pipeline rerun usually changes the
FITS headers but not the FITS data of raw data sets. In some cases
calibrated FITS data may change because the calculated geometry of an
observation has changed. See data set version-specific sections above
for significant exceptions to this general statement, i.e. changes to
pipeline processing, calibration processing, and data delivered.
Note that even if this is not a calibrated data set, calibration
changes are listed as the data will have been re-run and there will be
updates to the calibration files, to the documentation (Science
Operations Center - Instrument Interface Control Document:
SOC_INST_ICD) and to the steps required to calibrate the data.
Processing
==========
The data in this data set were created by a software data
processing pipeline on the Science Operations Center (SOC) at
the Southwest Research Institute (SwRI), Department of Space Operations.
This SOC pipeline assembled data as FITS files from raw telemetry
packets sent down by the spacecraft and populated the data labels
with housekeeping and engineering values, and computed geometry
parameters using SPICE kernels. The pipeline did not resample
the data.
Calibration
===========
Detailed information about calibration of MVIC data is available
in the SOC Instrument Interface Control Document (ICD) in the
DOCUMENT section of this data set. The MVIC calibration will only
be briefly summarized here; refer to the ICD for details about
what is summarized here.
The calibration of MVIC images comprises the following steps:
1) Remove bias and flat-field pattern
1.1) The result is an absolute calibration in raw DATA NUMBER units
(DN), with pixel values proportional to the incoming signal
2) Supply target source spectrum-dependent factors to scale from
absolute DN to scientific (flux and radiance) units; refer to the
DOCUMENT/SOC_INST_ICD*.* for more detail.
In addition, the calibration procedure calculates the error and
a data quality flag for each pixel and includes those results
in the calibrated data product as additional PDS OBJECTs (FITS
extensions) appended to the main OBJECT with the data image.
The quality flag PDS OBJECT is an image of values of the same
size as the main IMAGE product, with each quality flag pixel
mapped to the corresponding pixel in the main product. A quality
flag value of zero indicates a valid pixel; a non-zero value
indicates an invalid pixel (e.g. missing data outside the
window(s) of data intended to be downlinked).
Note that for windowed products, all pixels in an image are not
returned in the downlink telemetry. In the raw data, the pipeline
sets such pixels to zero DN (Data Number); the calibration processes
those zero-DN pixels as if they were real raw values, but also flags
them as missing data in the quality flag PDS OBJECT (FITS extension).
Displaying such images using an automatic stretch (contrast
enhancement) may result in a confusing result with the majority of
the displayed image appearing as an inverse of the calibration
(calibration of zero values); therefore the quality flag PDS OBJECT
should always be checked when looking at these data.
Note also that, at the time these data were created (late 2014), the
Science Operations Center (SOC) data processing pipeline did not have
the capability to merge multiple windows from a single observation.
As a result, in some cases one observation's products in raw and
and calibrated data sets may come from different windows. This is
normal, but it can have some noticeable side-effects:
i) Mismatches in windowing parameters between raw and calibrated
products for the same observation. Either the windowing parameters
differ, or one may be windowed and the other a non-windoed, full
image.
ii) START_TIME and STOP_TIME mismatches between versions of the same
TDI observations with different windows. The start and stop times
of TDI MVIC products are dependent on the start and stop lines of
the window: if the first line of the window is not the first line
of the observation, the START_TIME of the product will be delayed
from the start time of the observation; similarly the last line of
a window that is not the last line of the observation results in a
STOP_TIME that is earlier than the stop time of the observation.
Since there is only one version of each observation in any single
MVIC data set, this will not be noticeable within any single data
set. However, when comparing versions of the same observation from
raw and calibrated data sets, it is possible that the START_TIME
and STOP_TIME values for that observation will differ between the
data sets.
iii) The shift in start and stop times will also affect the
calculation of mid-observation times.
iv) The mid-observation time is used as the lookup in SPICE calls, so
the shift in time will affect calculated geometry values
As part of the preparation for the Pluto flyby in Spring, 2015, the SOC
pipeline was updated to all it to merge multiple windows and/or full
images of the same observation into a single product. so it is
expected that future MVIC data sets will have raw and calibrated
products with consistent windowing parameters, times and geometries.
A PDS OBJECT CALGEOM (FITS extension) with a correction for geometric
distortion, present in previous versions of MVIC data sets, has been
removed from these and future PDS calibrated data sets. Geometric
distorion will be addressed in higher-level products, as it involves
resampling the data.
Data
====
The observations in this data set are stored in data files using
standard Flexible Image Transport System (FITS) format. Each FITS
file has a corresponding detached PDS label file, named according
to a common convention. The FITS files may have image and/or table
extensions. See the PDS label plus the DOCUMENT files for a
description of these extensions and their contents.
This Data section comprises the following sub-topics:
- Filename/Product IDs
- Instrument description
- Other sources of information useful in interpreting these Data
- Visit Description, Visit Number, and Target in the Data Labels
Filename/Product IDs
--------------------
The filenames and product IDs of observations adhere to a
common convention e.g.
MC0_0123456789_0X530_ENG.FIT
^^^ ^^^^^^^^^^ ^^^^^ ^^^\__/
| | | | ^^
| | | | |
| | | | +--File type (includes dot)
| | | | - .FIT for FITS file
| | | | - .LBL for PDS label
| | | | - not part of product ID
| | | |
| | | +--ENG for CODMAC Level 2 data
| | | SCI for CODMAC Level 3 data
| | |
| | +--Application ID (ApID) of the telemetry data
| | packet from which the data come
| | N.B. ApIDs are case-insensitive
| |
| +--MET (Mission Event Time) i.e. Spacecraft Clock
|
+--Instrument designator
Note that, depending on the observation, the MET in the data filename
and in the Product ID may be similar to the Mission Event Time (MET)
of the actual observation acquisition, but should not be used as an
analog for the acquisition time. The MET is the time that the data are
transferred from the instrument to spacecraft memory and is therefore
not a reliable indicator of the actual observation time. The PDS label
and the index tables are better sources to use for the actual timing of
any observation. The specific keywords and index table column names for
which to look are
* START_TIME
* STOP_TIME
* SPACECRAFT_CLOCK_START_COUNT
* SPACECRAFT_CLOCK_STOP_COUNT
Instrument Instrument designators ApIDs **
=========== ================================== =============
MVIC MC0, MC1, MC2, MC3, MP1, MP2, MPF 0X530 - 0X54A *
* Not all values in this range are in this data set
** ApIDs are case insensitive
There are other ApIDs that contain housekeeping values and
other values. See SOC Instrument ICD (/DOCUMENT/SOC_INST_ICD.*)
for more details.
Here is a summary of the meanings of each instrument designator:
Instr
Dsgn. Description
===== ===========
MC0 MVIC, Color TDI, Red filter
MC1 MVIC, Color TDI, Blue filter
MC2 MVIC, Color TDI, Near-InfraRed (NIR) filter
MC3 MVIC, Color TDI, Methane (CH4) filter
MP1 MVIC, Panchromatic TDI CCD 1
MP2 MVIC, Panchromatic TDI CCD 2
MPF MVIC, Panchromatic frame (5024 pixels)
See SOC Instrument ICD (/DOCUMENT/SOC_INST_ICD.*) for details
Here is a summary of the types of files generated by each ApID
(N.B. ApIDs are case-insensitive) along with the instrument
designator that go with each ApID:
ApIDs Data product description/Prefix(es)
===== ===================================
0x530 - MVIC Panchromatic TDI Lossless (CDH 1)/MP1,MP2
0x53f - MVIC Panchromatic TDI Lossless (CDH 2)/MP1,MP2
0x531 - MVIC Panchromatic TDI Packetized (CDH 1)/MP1,MP2
0x540 - MVIC Panchromatic TDI Packetized (CDH 2)/MP1,MP2
0x532 - MVIC Panchromatic TDI Lossy (CDH 1)/MP1,MP2
0x541 - MVIC Panchromatic TDI Lossy (CDH 2)/MP1,MP2
0x533 - MVIC Panchromatic TDI 3x3 Binned Lossless (CDH 1)/MP1,MP2 *
0x542 - MVIC Panchromatic TDI 3x3 Binned Lossless (CDH 2)/MP1,MP2 *
0x534 - MVIC Panchromatic TDI 3x3 Binned Packetized (CDH 1)/MP1,MP2 *
0x543 - MVIC Panchromatic TDI 3x3 Binned Packetized (CDH 2)/MP1,MP2 *
0x535 - MVIC Panchromatic TDI 3x3 Binned Lossy (CDH 1)/MP1,MP2 *
0x544 - MVIC Panchromatic TDI 3x3 Binned Lossy (CDH 2)/MP1,MP2 *
0x536 - MVIC Color TDI Lossless (CDH 1)/MC0,MC1,MC2,MC3
0x545 - MVIC Color TDI Lossless (CDH 2)/MC0,MC1,MC2,MC3
0x537 - MVIC Color TDI Packetized (CDH 1)/MC0,MC1,MC2,MC3
0x546 - MVIC Color TDI Packetized (CDH 2)/MC0,MC1,MC2,MC3
0x538 - MVIC Color TDI Lossy (CDH 1)/MC0,MC1,MC2,MC3
0x547 - MVIC Color TDI Lossy (CDH 2)/MC0,MC1,MC2,MC3
0x539 - MVIC Panchromatic Frame Transfer Lossless (CDH 1)/MPF
0x548 - MVIC Panchromatic Frame Transfer Lossless (CDH 2)/MPF
0x53a - MVIC Panchromatic Frame Transfer Packetized (CDH 1)/MPF
0x549 - MVIC Panchromatic Frame Transfer Packetized (CDH 2)/MPF
0x53b - MVIC Panchromatic Frame Transfer Lossy (CDH 1)/MPF
0x54a - MVIC Panchromatic Frame Transfer Lossy (CDH 2)/MPF
* as of October, 2014, 3x3 modes have not been used
Instrument description
----------------------
Refer to the following files for a description of this instrument.
CATALOG
MVIC.CAT
DOCUMENTS
RALPH_SSR.*
SOC_INST_ICD.*
NH_RALPH_V###_TI.TXT (### is a version number)
Other sources of information useful in interpreting these Data
--------------------------------------------------------------
Refer to the following files for more information about these data
NH Trajectory tables:
/DOCUMENT/NH_MISSION_TRAJECTORY.* - Heliocentric
RALPH Field Of View definitions:
/DOCUMENT/NH_FOV.*
/DOCUMENT/NH_RALPH_V###_TI.TXT
Visit Description, Visit Number, and Target in the Data Labels
---------------------------------------------------------------
The observation sequences were defined in Science Activity Planning
(SAP) documents, and grouped by Visit Description and Visit Number.
The SAPs are spreadsheets with one Visit Description & Number per row.
A nominal target is also included on each row and included in the data
labels, but does not always match with the TARGET_NAME field's value in
the data labels. In some cases, the target was designated as RA,DEC
pointing values in the form ``RADEC=123.45,-12.34'' indicating Right
Ascension and Declination, in degrees, of the target from the
spacecraft in the Earth Equatorial J2000 inertial reference frame.
This indicates that either the target was a star, or the
target's ephemeris was not loaded into the spacecraft's attitude and
control system which in turn meant the spacecraft could not be pointed
at the target by a body identifier and an inertial pointing value had
to be specified as Right Ascension and Declination values. PDS-SBN
practices do not allow putting a value like RADEC=... in the PDS
TARGET_NAME keyword's value. In those cases the PDS TARGET_NAME value
is set to CALIBRATION. TARGET_NAME may be N/A (Not Available or Not
Applicable) for a few observations in this data set; typically that
means the observation is a functional test so N/A is an appropriate
entry for those targets, but the PDS user should also check the
NEWHORIZONS:OBSERVATION_DESC and NEWHORIZONS:SEQUENCE_ID keywords in
the PDS label, plus the provided sequence list (see Ancillary Data
below) to assess the possibility that there was an intended target.
These two keywords are especially useful for STAR targets as often
stars are used as part of instrument calibrations, and are
included as part of the sequencing description which is captured
in these keywords.
Ancillary Data
==============
The geometry items included in the data labels were computed
using the SPICE kernels archived in the New Horizons SPICE
data set, NH-J/P/SS-SPICE-6-V1.0.
Every observation provided in this data set was taken as a part of a
particular sequence. The sequence identifier (REQID) and
description are included in the PDS label
for every observation. N.B. While every observation has an associated
sequence, every sequence may not have associated observations. Some
sequences may have failed to execute due to spacecraft events (e.g.
safing). No attempt has been made during the preparation of this data
set to identify such empty sequences, so it is up to the user to
compare the times of the sequences to the times of the available
observations from INDEX/INDEX.TAB to identify such sequences.
Time
====
There are several time systems, or units, in use in this dataset:
New Horizons spacecraft MET (Mission Event Time or Mission Elapsed
Time), UTC (Coordinated Universal Time), and TDB Barycentric
Dynamical Time.
This section will give a summary description of the relationship
between these time systems. For a complete explanation of these
time systems the reader is referred to the documentation
distributed with the Navigation and Ancillary Information
Facility (NAIF) SPICE toolkit from the PDS NAIF node, (see
http://naif.jpl.nasa.gov/).
The most common time unit associated with the data is the spacecraft
MET. MET is a 32-bit counter on the New Horizons spacecraft that
runs at a rate of about one increment per second starting from a
value of zero at
19.January, 2006 18:08:02 UTC
or
JD2453755.256337 TDB.
The leapsecond adjustment (DELTA_ET = ET - UTC) was 65.184s at
NH launch, and the first four additional leapseconds occurred
at the ends of 12/2009, 06/2012, 06/2015, and 12/2016.
Refer to the NH SPICE data set, NH-J/P/SS-SPICE-6-V1.0, and the
SPICE toolkit documentation, for more details about leapseconds.
The data labels for any given product in this dataset usually
contain at least one pair of common UTC and MET representations
of the time at the middle of the observation. Other portions
of the products, for example tables of data taken over periods
of up to a day or more, will only have the MET time associated
with a given row of the table.
For the data user's use in interpreting these times, a reasonable
approximation (+/- 1s) of the conversion between Julian Day (TDB)
and MET is as follows:
JD TDB = 2453755.256337 + ( MET / 86399.9998693 )
For more accurate calculations the reader is referred to the
NAIF/SPICE documentation as mentioned above.
Reference Frame
===============
Geometric Parameter Reference Frame
-----------------------------------
Earth Mean Equator and Vernal Equinox of J2000 (EMEJ2000) is the
inertial reference frame used to specify observational geometry items
provided in the data labels. Geometric parameters are based on best
available SPICE data at time of data creation.
Epoch of Geometric Parameters
-----------------------------
All geometric parameters provided in the data labels were computed at
the epoch midway between the START_TIME and STOP_TIME label fields.
Software
========
The observations in this data set are in standard FITS format
with PDS labels, and can be viewed by a number of PDS-provided
and commercial programs. For this reason no special software is
provided with this data set.
Contact Information
===================
For any questions regarding the data format of the archive,
contact
New Horizons RALPH Principal Investigator:
Alan Stern, Southwest Research Institute
S. Alan Stern
Southwest Research Institute (SwRI)
Department of Space Studies
1050 Walnut Street, Suite 400
Boulder, CO 80302
USA
|
| CONFIDENCE_LEVEL_NOTE |
Confidence Level Overview
=========================
During the processing of the data in preparation for
delivery with this volume, the packet data associated with each
observation were used only if they passed a rigorous verification
process including standard checksums.
In addition, raw (Level 2) observation data for which adequate
contemporary housekeeping and other ancillary data are not available
may not be reduced to calibrated (Level 3) data. This issue is raised
here to explain why some data products in the raw data set,
NH-A-MVIC-2-KEM1-V4.0,
may not have corresponding data products in the calibrated data set,
NH-A-MVIC-3-KEM1-V4.0.
Data coverage and quality
=========================
Every observation provided in this data set was taken as a part of a
particular sequence. A list of these sequences has been provided in
file DOCUMENT/SEQ_MVIC_*.TAB. N.B. Some sequences provided may have
zero corresponding observations.
Refer to the Confidence Level Overview section above for a summary
of steps taken to assure data quality.
During functional tests, some TDI images with prefixes like mc0,
mc1, mc2, mc3, mp1, and mp2 will have a height (PDS keyword LINES)
of less than 100 lines (values of 32, 33, 52, and 96 are common)
and a width (LINE_SAMPLES) of 5024, giving the impression of a
noodle-like image. These images were only generated to confirm
proper operation of MVIC and are unlikely to have any scientific
value. Functional test images can usually be identified by the
case-insensitive string 'func' in the value of the
NEWHORIZONS:SEQUENCE_ID keyword in the PDS label.
Observation descriptions in this data set catalog
=================================================
Some users will expect to find descriptions of the observations
in this data set here, in this Confidence Level Note. This data
set follows the more common convention of placing those
descriptions under the Data Set Description (above, if the user is
reading this in the DATASET.CAT file) of this data set catalog.
Caveat about TARGET_NAME in PDS labels and observational intent
===============================================================
The downlink team on New Horizons has
created an automated system to take various uplink products, decode
things like Chebyshev polynomials in command sequences representing
celestial body ephemerides for use on the spacecraft to control
pointing, and infer from those data what the most likely intended
target was at any time during the mission. This works well during
flyby encounters and less so during cruise phases and hibernation.
The user of these PDS data needs to
be cautious when using the TARGET_NAME and other target-related
parameters stored in this data set. This is less an issue for the
plasma and particle instruments, more so for pointing instruments.
To this end, the heliocentric ephemeris of the spacecraft, the
spacecraft-relative ephemeris of the inferred target, and the
inertial attitude of the instrument reference frame are provided
with all data, in the J2000 inertial reference frame, so the user
can check where that target is in the Field Of View (FOV) of the
instrument.
Finally, note that, within the FITS headers of the data products,
the sequence tables, and other NH Project-internal documents used
in this data set and/or inserted into the data set catalog,
informal names are often used for targets instead of the canonical
names required for the TARGET_NAME keyword. For example, during
the Pluto mission phase, instead of the TARGET_NAME '15810 ARAWN
(1994 JR1)' there might be found any of the following: 1994JR1;
1994 JR1; JR1. For all values where the PDS keyword TARGET_NAME
is used (e.g. in PDS labels and in index tables), the canonical,
PDS-approved names are used (if not, please bring this to the
attention of PDS so it can be rectified). However, within the
context of this data set, these project abbreviations are not
ambiguous (e.g. there is only one NH target with 'JR1' in its
name), so there has been, and will be, no attempt to expand such
abbreviations where they occur outside formal PDS keyword values.
Review
======
This dataset was peer reviewed and certified for scientific use by
the PDS.
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